A NATION CHALLENGED: THE TOLL; Taking Account of the Dead, Feeling Weight of History

In the hours after the World Trade Center's twin towers fell, Mayor Rudolph W. Giuliani predicted that the number of people dead in the ruins would be ''more than any of us can bear ultimately.'' The weeks since then have proven the mayor grimly correct.

But the process of determining precisely how many people perished, a sad accounting that has deep meaning for individual families, the public and history, has proven to be complicated and hard to control, city officials now say. The publicly announced numbers of the missing and presumed dead have swung wildly, leaping by hundreds one day and falling by hundreds days later.

This week, though, the officials in charge of tracking the dead and the missing said they think they are closing in on what they regard as a responsible final total. They now have detailed reports on about 4,000 people who are presumed to have died in the Sept. 11 terrorist attack. And while they may not release a final count for a few weeks, they now expect the final list of fatalities to include 4,500 to 5,000 people.

''I don't believe you'll see dramatic reductions in the numbers we have now,'' Deputy Mayor Joseph J. Lhota said. ''We are monitoring it every day. We are trying to make it as scientific as possible.''

In interviews over the last several days, the officials involved -- 250 police officers and hundreds from the medical examiner's office and other agencies -- talked about the details of the process of counting the missing and confirming the dead, the confusion that resulted, and their dedication to getting right a count that will affect everything from death claims to history books.

''With the blast, the tremendous heat, the collapse, it means, unfortunately, we are not going to find a lot of people,'' said Chief Charles V. Campisi, who as head of the Police Department's Internal Affairs Bureau is the top official in charge of the count. ''So it is imperative that we know just who is missing.''

The intent, from the start, was to collect missing-person reports centrally through a New York Police Department hot line. But almost immediately, state and local police departments in New York State, New Jersey and Connecticut, as well as companies with offices in the World Trade Center complex, local relief agencies and diplomats representing countries from across the globe, started to compile their own lists.

The city's police officers entered the different lists of names into a single computer. With speculation quickly flaring after it was learned that the city had 30,000 body bags available, Mr. Giuliani sought to reassure the public with the city's first estimate, released on Sept. 13. It put the missing count at 4,763.

But hundreds of new reports were still pouring in from police departments, relief workers, tenants and particularly foreign nations. By Sept. 18, the count of the missing had ballooned to 6,030; two days later it reached 6,333. By Sept. 24, it had hit 6,453.

Up to that point, the city had tried but not succeeded in preventing people from being counted more than once and in limiting bogus reports or filings made on slim suspicions. People were added to the computer list as long as the new name and information did not directly match someone on it.

For instance, some of the people on the list, the city now says, were perhaps injured or could not get home in the day after the attack; they were safely at home, but had not called in to tell the authorities to remove them from the list. Other people who simply had not returned phone calls to relatives overseas were added when their embassies filed lists.

The problem, officials said, was that in a complex as immense as the World Trade Center -- where visitors, tourists, commuters, shoppers and workers come and go -- there was no easy way to rule out a missing-person report immediately.

''We had names of people who may have been missing for three months, who may have been in the United States, maybe in New York, and nobody from their country back home had heard from them,'' Police Commissioner Bernard B. Kerik said.

But roughly 10 days after the attack, city officials, with their own official number of dead and missing at more than 6,400, recognized that they had probably allowed the list to grow too much. Initial checks of reports from embassies had found that many were grossly inaccurate.

The officials began to cull the computer list to remove duplications, eliminate those erroneously reported and root out fraud, acknowledging that the early effort by workers to cross-check had been imperfect.

Mr. Kerik had already been using officers from the Internal Affairs Bureau to do the counting. The bureau's officers, normally charged with the delicate task of investigating police misconduct charges, had been working at three primary locations around the city.

About 150 officers were sent to a Hudson River pier that the city had converted into a family center to tend to the needs of victims' relatives. There the officers sat in rows of cubicles -- each with a desk, a computer, a telephone and a box of Kleenex -- to work with relatives to compile a detailed report on each missing person. Others were assigned to the morgue, where they helped monitor the counting of the confirmed dead.

But the culling work was reserved in large part for the others who remained at Internal Affairs Bureau headquarters, where they worked the telephones to try to track down relatives of every person reported missing, particularly those who had not shown up at the family center.

The accuracy of the list has profound implications for those trying to collect insurance, for those seeking charitable assistance and federal benefits and, city officials acknowledge, for the accepted history of the attack.

Some of the work of sorting duplications and errors was relatively simple at first. A missing man with the last name of Burns, for example, might also have been listed as Burnes, Chief Campisi said. First names and last names of some, particularly foreigners, were at times reversed.

In one case, a woman had been reported missing a dozen times, but because different people had provided different addresses and contact numbers when calling in the reports, the repetitious claims were not noticed at first. The police also identified two fraudulent claims.

As of last evening, the city's list of the identified dead stood at 321; its count of the missing stood at 4,974.

City officials said they now had much more confidence in the accuracy of the list of missing. But they are still working through about 1,000 of those claims to ensure that each is valid and they expect the number to continue to drop, if modestly.

''I think it will be less than 5,000, but only by the grace of God,'' Chief Campisi said.

The work is becoming even more intensive, and in a certain number of cases detectives will be assigned to confirm that some individuals listed actually were at the World Trade Center at the time of the attack.

Looking back over the last 25 days, officials say they realize that the numbers have fluctuated erratically, and that the growing numbers had an impact on how the world measured the severity of the event. City officials, as they continued to revise the information again and again, said the numbers could fall even below their expectations. But no one, at least in the United States, had ever embarked on a task so complex. What matters, they added, is that the final number is accurate, a goal they were confident they could achieve.

''This is the biggest attack on United States soil in our history,'' Mr. Kerik said. ''So the count must be as detailed and accurate as possible, because it, too, will go down in our history. That part may not have hit all of our people yet, but that is another reason it has to be done right.''